1. Field of the Invention
The present invention relates to a process for the manufacture of an olefin oligomer, particularly, an olefin oligomer suitable for use as synthetic lubricant base fluids wherein catalysts can be recovered while maintaining the activities thereof.
2. Description of the Related Art
An olefin oligomer prepared by polymerizing an olefin, particularly an alpha-olefin having 6 to 12 carbon atoms, is useful as synthetic lubricant base fluids.
In a known process for the production of such an alpha-olefin oligomer, the polymerization is carried out by using boron trifluoride and a boron trifluoride-alcohol complex as catalysts. Reference is made to Japanese Examined Patent Publications (KOKOKU) No. 59.53244, No. 60-37159, and No. 61-326, and U.S. Pat. No. 3,382,291 and U.S. Pat. No. 3,780,128.
The above conventional process for the production of the olefin oligomer using the above-mentioned catalysts is widely used, because not only the oligomer can be obtained in a high yield, but also the reaction can be controlled to obtain a desired oligomer, and the like.
In the above conventional process, however, the polymerization product is treated by adding an alkaline or water to deactivate and discard the catalysts. Hitherto, there was no satisfactory process for recovering the catalysts. For example, this can be done by allowing the polymerization product to stand, whereby the catalysts are separated therefrom and recovered. However, the product must be allowed to stand for a long time, and the activity of the recovered catalysts is lowered.